Rechargeable energy storage units are substantially based on the principle of electrochemical cells, i.e. the redox-based conversion of chemical into electrical energy or vice versa. In the process, oxidizing agents, for example oxygen ions from atmospheric oxygen, are conventionally formed on a positively charged electrode, and supplied to the negative electrode by an electrolyte which is arranged between the positive and a negative electrode and is appropriately permeable to the oxidizing agent, i.e. the oxygen ions which are formed for example.
In the case of rechargeable energy storage units, the material to be oxidized, i.e. the reducing agent, is a direct or indirect constituent of the energy storage unit, for which reason energy may be drawn from the energy storage unit until the reducing agent has been wholly oxidized. Only after a subsequent charging process of the energy storage unit with electrical energy via an external source can the energy storage unit again be discharged. Further details regarding the mode of operation of such rechargeable energy storage units are well known.
Generic energy storage units with oxygen ion-conducting electrolytes are known to have working ranges at temperatures of above 500° C., since only a correspondingly high temperature provides satisfactory conditions in particular in relation to the activity or ion conductivity of the materials used, in order to be able to allow the corresponding processes, such as for instance the electrochemical reduction of atmospheric oxygen to oxygen ions and moreover the movement thereof through the electrolytes, to proceed properly.
Owing to exposure elevated thermal loads, performance is regularly impaired in rechargeable energy storage means in particular with regard to the electrode, which is connected as an anode in discharging operation and, as a rule, is formed of a porous network of metallic particles or is associated operationally with such particles, as a result of degradation caused in particular by agglomeration of metallic particles, which results in a reduction in the active surface area of the electrode material and moreover has a negative effect on the efficiency and service life of the energy storage unit.